Plant images

Plant biology

Stems of Noogoora burr are blotched or streaked with purple, somewhat zig-zagged and covered with short, coarse, upward-pointing hairs.

Leaves

The leaves of Noogoora burr are dark green on the upper surface. The lower leaves grow in opposite formation. The upper leaves alternate and are similar in shape to grape or maple leaves. They grow to 15 cm diameter and are dissected into 3-5 large lobes which are coarsely toothed. The leaves have a rough texture with minute bristles, glandular hairs and prominent veins. They grow on grooved stalks 10-20 cm long, which along with the veins are a reddish or purple or green colour.

Flowers

Noogoora burr flowers are inconspicuous. They are formed in clusters consisting of male and female flowers in leaf axils towards the ends of the branches.

Fruit

Noogoora burr fruit is a brown, hard, woody burr when mature which is armed with numerous hooked spines and two terminal beaks. The burrs form in clusters of 2-13 and are 1.2-2.5 cm long with straight to curved beaks.

Seeds

Seeds of Noogoora burr are brown or black. Two seeds occur in each burr and are 6-10 mm long, one larger than the other and flattened on one side.

Roots

The Noogoora burr plant has a stout tap-root and extensive lateral roots.

Growth and lifecycle

Method of reproduction and disperal

Noogoora burr plants are well equipped for dispersal because of their hooked spines which readily entangle in wool, fur, bags and animal hair.

Air cavities around the seeds assist the burrs to float on water, so much of their spread in Australia has been along waterways.

Burrs are commonly spread in agricultural seeds of summer crops such as maize, sorghum and sunflower. Burrs may also be spread through road construction activities.

Seedbank propagule persistence

A single, vigorous, open-growing plant can produce as many as 11,000 burrs. It has been calculated that provided no new burrs are introduced to an area, it would take six years to reduce the viable seed population in the soil to less than one per cent. Therefore, any control site must be monitored for longer than this period.

A close watch must be kept on re-infestation through flooding or the introduction of contaminated stock.

Preferred habitat

Noogoora burr prefers unshaded, warm situations in temperate regions, usually on fertile soils. They occur as weeds of cultivation, grazing land and wasteland that is subject to summer rainfall, flooding or irrigation. They extend into semi-arid areas by establishing close to watercourses.

It grows best in open, unshaded areas and dislikes dense crowding or intense competition.

Noogoora burr tolerates intermittent water logging, flooding at all growth stages and salinity ranges from moderate to quite high, depending on the ecotype.

Growth calendar

The icons on the calendar below represent the times of year for flowering, seeding, germination, the dormancy period of Noogoora burr and also the optimum time for treatment.

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Flowering

Seeding

Germination

Dormancy

Treatment

Impact

Impact on ecosystems and waterways

This plant is common around waterholes, along floodplains, canals, ditches, creek flats, riparian areas, river terraces, and other moist places.

On disturbed sites it can establish as dense patches. Noogoora burr is most likely to affect ground level flora, grass, herbs and forbs.

Agricultural and economic impacts

Noogoora burr is a significant weed of crops and pastures, forms very dense stands which are completely dominant and cover entire paddocks.

In Victoria, it affects tomato, sunflower and summer crops and is a weed of importance in the dried fruit industry.

The burrs may become entangled in sheep's wool and are a problem to shearers.

Noogoora burr is a major cause of 'vegetable fault' in wool. The burrs often mat the wool, particularly under the neck and on the belly of sheep, which results in serious damage to carding machines. Burrs cannot be mechanically removed and the wool must be carbonised. This process imposes an additional cost on production.

Burrs lodged in the hooves of animals cause irritation, infection and lameness. They can seriously reduce carrying capacity, and in some cases infestations may be so dense that sheep have difficulty accessing watering points.

Seeds and seedlings are poisonous to animals, particularly cattle and pigs.

Social value and health impacts

Noogoora burr can cause dermatitis in humans and farm animals. Pollen from the plant may cause hay fever.

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